Skip to main content

Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

See other formats



or of water alone when volatile solvent is absent, may be determined as
in stiff lubricants (q.v., 3).

3.  Detection and Determination of the Soaps (Fatty Acids and
Alkalies).—A preliminary test is made to ascertain whether ammonia or
a fixed alkali is present.   Ammonia is detected by the odour and reaction
of the vapour emitted when a few grams of the oil are heated in a dish ;
a fixed residue remaining after calcining indicates the presence of fixed

(a) IN PRESENCE OF AMMONIA. The ammonia is determined by titrating
the aqueous emulsion of the oil with N/2-hydrochloric acid in presence of
methyl orange. From the amount of ammonia found, the quantity of
fatty acids (regarde.d as oleic acid) combined with it is calculated (i gram
NH3 = 16-542 grams of C18H3402). The total fatty acids are then deter-
mined by boiling the emulsion of the oil with a known quantity, in excess,
of N/io-sodium hydroxide solution and titrating the excess of alkali with
N/io-acid. The alkali used gives the total fatty acids (calculated as oleic
acid) and this quantity, less the combined fatty acids, gives the free fatty

(6) IN PRESENCE OF FIXED ALKALI. The free acids are determined by
direct titration of the acidity in the usual way, and the total fatty acids
by decomposing the soaps with hydrochloric acid, extracting the fatty acids
with ether, washing the ethereal layer with water until free from hydrochloric
acid, and titrating the acidity of this layer. The combined fatty acids are
then given by difference. The aqueous layer is tested qualitatively for
alkalies (see also Stiff Lubricants, 5).

the fatty acids combined with it, and the free fatty acids are determined
as in (a), the total fatty acids as in (b) and the fatty acids combined with
the fixed alkali by difference.

4.  Detection of Unsaponifiable Substances.—See Stiff Lubricants, 7.

A.c.(tallow, wool fat, wax). Adhesive lubricants for belting con-